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Z–Scheme heterojunction ZnO-Au-ZnAl2O4: Bridge-type hot carrier transfer and reaction kinetics in the photodegradation of catechol

Guanhua Zhang,Tiantian Dai,Yue Meng,Lianyang Zhang,Chao Yang,Guoxiang Pan,Zheming Ni,Shengjie Xia

Z-scheme heterojunction catalysts are novel photocatalytic materials with wide application prospects because of their promise for the engineering of band structure to achieve high-speed hot carrier-transfer and strong redox tunability. A bridged-Au Z-scheme heterojunction catalyst (ZnO-Au-ZnAl 2 O 4 ) was synthesized using layered double hydroxides (LDHs) as the backbone. The atomistic and architectural structures, elemental composition and and visible-light absorption of as-prepared photocatalysts were systematically investigated and characterized. The presence of Z-scheme heterojunctions in ZnO-Au-ZnAl 2 O 4 can significantly improve the photocatalytic activity under visible light irradiation with a reaction rate constant of 0.5503 h −1 (ZnO-Au(2%)-ZnAl 2 O 4 ), 27.2 times that of pure ZnO (0.0202 h −1 ) and 9.8 times that of ZnO-ZnAl 2 O 4 (0.0389 h −1 ). We further investigated the reaction kinetics of the heterostructure catalyst in the photodegradation of catechol , where the effect of the catalyst dosage, initial pH, irradiation intensity and reaction temperature were discussed. Based on the mechanism study in the capture and detection of photo-generated radicals and the calculation of band structures by DFT (work function), the successful construction of bridged-Au Z-scheme heterojunction was further proven. Au nanoparticles sandwiched between ZnO and ZnAl 2 O 4 play a vital role for the formation of a built-in electric field (BIEF) between ZnO and ZnAl 2 O 4 , which can significantly facilitate the transfer of hot carriers in the photocatalytic system.